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24 lines
1.3 KiB
Plaintext
24 lines
1.3 KiB
Plaintext
created: 20150124182127000
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modified: 20201103111044922
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tags: [[Filter Syntax]]
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title: Filter Step
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type: text/vnd.tiddlywiki
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<$railroad text="""
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[:"!"]
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[: [[operator|"Filter Operators"]] [:":" suffix] ]
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[[parameter|"Filter Parameter"]]
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"""/>
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A <<.def step>> represents a single operation within a [[filter|Filter Syntax]].
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In programming terms, it is akin to a function call to which [[the step's input|Filter Run]] is passed as an implicit parameter. A step's output is a [[selection|Title Selection]] that contributes to a [[run|Filter Run]] and hence to the entire [[filter expression|Filter Expression]] that contains it.
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The step's <<.def operator>> is drawn from a list of [[predefined keywords|Filter Operators]], which can be extended by plugins. Any unrecognised operator is treated as if it was the suffix to the <<.olink field>> operator. If a step's operator is omitted altogether, it defaults to `title`.
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The <<.def suffix>> is additional text, often the name of a [[field|TiddlerFields]], that extends the meaning of certain operators.
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Many steps require an explicit <<.def parameter>> value, also known as an <<.def operand>>, that further defines what the step is to do.
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<<.from-version "5.1.23">> Some steps accept multiple parameters which are separated by a ` , ` character.
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